1. Field of the Invention
The present invention relates to a continuous processing method and apparatus for sensitive materials having different sizes in a thermal developing apparatus.
2. Description of the Related Art
A continuous process in the thermal developing apparatus has conventionally been carried out in a newspaper publishing company. In that case, the process has been a continuous process for equal sized sensitive materials.
Moreover, a process for sensitive materials having various sizes has conventionally been carried out in the thermal developing apparatus. In that case, an offline process is carried out. More specifically, in the case in which a sensitive material having a different size is to be thermally developed after one sensitive material is completely developed thermally, a cassette including a sensitive material having a desired size is replaced with another cassette in the apparatus, thereby carrying out the thermal development.
In this respect, conventionally, it has not been necessary to carry out the continuous process for sensitive materials having various sizes in the thermal developing apparatus. Under the present circumstances, therefore, the same continuous process is not performed. In the invention, there is performed the continuous process for sensitive materials having various sizes in the thermal developing apparatus which has not been carried out. In that case, moreover, an image can be prevented from being deteriorated.
In the case in which thermal developing sheets (hereinafter referred to as sheets) which have the same size are to be continuously developed thermally, a change in the temperature of a heating member for heating the sheet and a change in a temperature distribution in the direction of the width of the sheet can be set to have such a level as not to deteriorate the quality of an image by maintaining the sufficient heat capacity of the heating member or an optimum temperature control method.
In the case in which sheets having different sizes (widths, lengths) are to be continuously developed thermally, however, the change in the temperature of the heating member, particularly, the change in the temperature distribution in the direction of the width of the sheet becomes remarkable even if the sufficient heat capacity is maintained in the heating member. Consequently, it has been found that the quality of an image is deteriorated. More specifically, according to the experiment carried out by the applicant, a countermeasure can be taken by increasing the heat capacity of the heating member in the case of the continuous process for sheets having different sizes and lengths, and the following problem arises in the case of the continuous process for sheets having different widths.
In the case in which the heating member is particularly constituted by a rotor such as a nip roller, it can be proposed that a heater is divided into a plurality of portions in the direction of the width of the heating roller and a plurality of temperature sensors are also provided in the direction of the width of the sheet to control the temperatures of the temperature sensor and the heater in respective corresponding portions independently of others. However, the apparatus becomes complicated and large-scaled so that a cost is increased.
In the case in which the heating member is a heating roller comprising a rotor such as a nip roller, particularly, it is preferable that the temperature sensor should be provided in a central portion in the direction of the width of the heating roller, that is, a sheet passage region because the temperature of the sheet can be detected accurately. However, the temperature sensor actually breaks down easily due to the jam of the sheet. Accordingly, the reliability of performance cannot be obtained. Therefore, the temperature sensor is not provided in the central portion in the direction of the width of the heating roller.
Consequently, the temperature sensor is not provided in the sheet passage region but on the outside of the sheet passage region on the heating roller such that the temperature sensor is not involved in a trouble such as the jam of the sheet. In consideration of the case in which the sheets having various sizes pass, moreover, the temperature sensor is provided in the vicinity of a passage region for a sheet having a maximum size outside the same passage region. An error between an actual temperature in the central portion of the sheet on the heating roller and a temperature detected by the temperature sensor in the vicinity of the passage region is previously measured to create a correction table, and the output value of the temperature sensor is corrected based on the correction table and is thus used. Consequently, the temperature in the central portion of the sheet can be detected without being involved in a trouble such as the jam of the sheet.
In the case in which the temperature sensor is thus provided in a very limited position on an end in the direction of the width of the sheet having a maximum size over the rotor such as a nip roller, the temperature of the heating roller which is reduced by the thermal developing process of the sheet can be detected accurately and a timing in which a reference temperature is recovered can be precisely taken because a space between the end of the sheet having a large size and the temperature sensor is small. Accordingly, the temperature control can be carried out accurately. A second sheet to be thus developed thermally after the execution of the accurate temperature control can be developed thermally with a satisfactorily high quality of an image irrespective of a size.
In the case of a sheet having a small size, however, a distance between a sheet end passing through the heating roller and the temperature sensor is great and a reduction in the temperature of the heating roller in a portion through which the sheet passes cannot be accurately detected by means of the temperature sensor provided on the end so that a temperature detected by the temperature sensor is higher. Thus, although the temperature in the central portion of the heating roller is actually low and is not recovered to an optimum developing temperature after the sheet having a small size passes, the temperature detected by the temperature sensor has already been recovered to the reference temperature. Therefore, an instruction for delivering a second sheet is given to start the thermal development. For this reason, the sheet is thermally developed in a state in which the temperature in the central portion in the direction of the width of the heating roller is still low. From the experiment carried out by the applicant, consequently, it has been found that the quality of an image is deteriorated in the central portion as compared with the end of the sheet.
In order to solve the problem, it is an object of the invention to provide a thermal developing method and apparatus in which the quality of an image can be prevented from being deteriorated in a central portion as compared with the end of a sheet, that is, the picture quality can be prevented from being deteriorated by a change in the temperature of a heating member when sheets having various sizes are to be continuously processed.
In order to attain the object, a first aspect of the invention is directed to a thermal developing method for continuously and thermally developing thermal developing sheets which have a latent image formed thereon by exposure and various sizes, wherein a minimum temperature recovery time required for thermally developing a next thermal developing sheet is determined from physical information about a thermally developed sheet, and the next thermal developing sheet is started to be developed after the minimum temperature recovery time passes.
A second aspect of the invention is directed to a thermal developing method for continuously and thermally developing thermal developing sheets which have a latent image formed thereon by exposure and various sizes, wherein minimum temperature recovery times required for thermally developing a next thermal developing sheet are determined from physical information about a thermally developed sheet and physical information about the next thermal developing sheet, respectively, and the next thermal developing sheet is started to be developed after either of the minimum temperature recovery times which is greater passes.
A third aspect of the invention is directed to the thermal developing method according to the first or second aspect of the invention, wherein the physical information is constituted by a combination of at least one of a dimension in a direction of a length, a dimension in a direction of a width, a thickness and a material of the thermal developing sheet.
A fourth aspect of the invention is directed to a thermal developing method for continuously and thermally developing thermal developing sheets which have a latent image formed thereon by exposure and various sizes, comprising the steps of determining a minimum temperature recovery time required for thermally developing a next thermal developing sheet from a size of a thermally developed sheet, measuring a time required until a rear end of the thermal developing sheet is completely developed and a tip of the next thermal developing sheet is then started to be developed, comparing the required time with the minimum temperature recovery time, and starting to develop the next thermal developing sheet if the required time is equal to or greater than the minimum temperature recovery time as a result of the comparison.
A fifth aspect of the invention is directed to a thermal developing method for continuously and thermally developing thermal developing sheets which have a latent image formed thereon by exposure and various sizes, comprising the steps of acquiring information about a size of a next thermal developing sheet before a developing process, measuring a time required until a rear end of the thermal developing sheet is completely developed and a tip of the next thermal developing sheet is then started to be developed, determining a minimum temperature recovery time required for thermally developing the next thermal developing sheet from a size of a thermally developed sheet and a size of the next thermal developing sheet, comparing the required time with the minimum temperature recovery time, and starting to develop the next thermal developing sheet if the required time is equal to or greater than the minimum temperature recovery time as a result of the comparison.
A sixth aspect of the invention is directed to a thermal developing apparatus for continuously and thermally developing thermal developing sheets which have a latent image formed thereon by exposure and various sizes, comprising sheet tip required time measuring means for measuring a time required until a rear end of the thermal developing sheet is completely developed and a tip of a next thermal developing sheet is then started to be developed, minimum temperature recovery time determining means for determining a minimum temperature recovery time required for thermally developing the next thermal developing sheet from a size of a thermally developed sheet, and comparing means for comparing the required time measured by the sheet tip required time measuring means with the minimum temperature recovery time determined by the minimum temperature recovery time determining means.
A seventh aspect of the invention is directed to a thermal developing apparatus for continuously and thermally developing thermal developing sheets which have a latent image formed thereon by exposure and various sizes, comprising sheet size information acquiring means for acquiring information about a size of a next thermal developing sheet before a developing process, sheet tip required time measuring means for measuring a time required until a rear end of the thermal developing sheet is completely developed and a tip of the next thermal developing sheet is then started to be developed, minimum temperature recovery time determining means for determining a minimum temperature recovery time required for thermally developing the next thermal developing sheet from a size of a thermally developed sheet and a size of the next thermal developing sheet, and comparing means for comparing the required time measured by the sheet tip required time measuring means with the minimum temperature recovery time determined by the minimum temperature recovery time determining means.
An eighth aspect of the invention is directed to the thermal developing apparatus according to the sixth or seventh aspect of the invention, wherein the next thermal developing sheet is started to be developed if the required time is equal to or greater than the minimum temperature recovery time as a result of the comparison of the comparing means.
Thus, according to the invention, by having a time required for the heating member to recover to such a level that a picture quality is not deteriorated after a thermally developing sheet of each of various predetermined sizes is thermally developed, the information about the size of the sheet as a parameter is obtained to set the time required for causing the next thermal developing sheet to stand by for each size. Also in the case in which the sheets having various sizes are to be continuously processed, accordingly, the thermal development can be carried out without deteriorating the picture quality due to a change in the temperature of the heating member.